Manganese alloys



United States atent O MANGANESE ALLOYS Reginald S. Dean, Hyattsville, Md., assignor to Chicago Development Corporation, Riverdale, Md, a corporation of Delaware N Drawing. Filed Jan. 22, 1959, Ser. No. 788,269

2 Claims. (Cl. 75134) This invention relates to corrosion resistant alloys having high coefficient of expansion and high electrical resistance. It relates particularly to alloys containing a major proportion of manganese and lesser amounts of nickel, and one or more of the metals chromium and copper.

Alloys of the nominal composition 72% Mn, 18% Cu, 10% Ni are widely used in the art because of their high expansion and high resistance. These alloys, however, are not fully corrosion resistant and their high resistance is accompanied by a moderately high temperature coefiicient of resistance. It is the aim of the present invention to provide alloys of equally high expansion and resistance, but with lower temperature coeflicient of resistance and improved corrosion resistance. I have found that alloys of 72% Mn, 1-14% nickel, 418% copper, up to 9% chromium and up to 3% aluminum have improved properties in this respect. Preferred compositions within the composition range of my invention are:

(1) 72% Mn, 10% Ni, 17% Cu, 1% Al (2) 72% Mn, 10% Ni, 16% Cu, 1% Al, 1% Cr (3) 72% Mn, 14% Ni, 9% Cr, Cu

(4) 72% Mn, 13% Ni, 9% Cr, 5% Cu, 1% A1 listed may be varied within the limits of the composition of my invention when it is desired to improve certain properties at the expense of others. In general, increasing aluminum increases the coefficient of expansion, while increasing chromium increases corrosion resistance.

Having now described my invention in its general terms, I will now illustrate my invention by specific examples.

Example I In this example, I melt electrolytic manganese with electrolytic nickel, chromium and copper in a magnesite crucible in an induction furnace in the approximate proportions of 72% Mn, 14% Ni, 9% Cr and 5% Cu. I cast the alloy in a chill mold and hot roll at 900-950 C. to A1" rod. I then reduce this rod by drawing through dies with frequent anneals to 10 mil wire. I beat this wire for 4 hours in an inert atmosphere of N2 at 750 C. The wire was then found to be ductile and have a specific resistance of 192 microhm Cm and a temperature coefiicient of resistance from 20-150" C. of 0.000008 per C. The wire by actual analysis showed 71.86% Mn, 13.13% Ni, 10.93% Cr and 4.08% Cu.

2 Example 11 In this example, I proceed as in Example I except that instead of electrolytic manganese, I use aluminothermic manganese containing 1.8% A1. The wire produced had a specific resistance of 198 microhm Cm and a temperature coefiicient of resistance from 20-150 C. of 0.00002. The loss in weight on shaking in 10% salt solution for 96 hours was 0.28 mg. as compared with 0.56 mg. for

for the product of Example I. Both samples remained bright and were not embrittled by the salt water treatment. The analysis of this wire was 71.90% Mn, 13.05% Ni, 10.95% Cr, 4.10% Cu and a trace of iron.

Example III I prepare an alloy as in Example I except that the nominal composition is 72% Mn, 17% Cu, 10% Ni and 1% Al. This alloy is reduced to 4: inch rod and an.

nealed at 1600" F. The coefiicient of linear expansion is found to be 30 10- C. at 20 C. as compared to a commercial 72-18-10 rod which had a coefiicient of 27.2 lO- The specific electrical resistance of this rod was 178 microhm Cm and the temperature coefiicient of electrical resistance was 0.00015 per C. The actual analysis of this rod was 71.96% Mn, 17.96% Cu, 9.96% Ni and 1.2% A1. A corrosion test of this rod in 1% salt solution showed a weight loss of /2 that of standard 72-18-10 under the same conditions.

Example IV Example V I prepare the alloy of Example IV except that instead of electrolytic manganese, I use aluminothennic manganese with 1.87% A1. A rod prepared from this alloy had a coefiicient of linear expansion of 30.2 10 C. Weight loss on corrosion testing in salt water was less than 1% of standard 72-18-10. The actual analysis of the alloy was 71.92% Mn, 14.65% Cu, 10.75% Ni, 2.05% I Cr, 1.3% A1 and a trace of iron.

What is claimed is:

1. An alloy consisting of about 72% Mn, 14% Ni, 9% Cr, 5% Cu, heated at 750 C. for several hours whereby to reduce the temperature coeflicient of resistance to.

about 0.00002 in the range 20150 C.

2. An alloy consisting of about 16.518% Cu, 9.5- 10.5% Ni. 0.54% Al, and about 72% Mn having a coefiicient of linear expansion at 20 C. of about 30 10- C.

References Cited in the file of this patent UNITED'STATES PATENTS 2,250,470 Dean July 29, 1941 2,287,888 Kroll June 30, 1942 FOREIGN PATENTS 537,333 GreatBritain ..-"u...- June 18, 1941 

2. AN ALLOY CONSISTING OF ABOUT 16.5-18% CU, 9.510.5% NI. 0.5-3% AL, AND ABOUT 72% MN HAVING A COEFFICIENT OF LINEAR EXPANSION AT 20*C. OF ABOUT 30X10-6/*C. 